Means and techniques useful in prestressing concrete structures

ABSTRACT

In wrapping wire around a concrete tank to prestress the same, a carriage is caused to travel around the tank by a motor-driven sprocket wheel thereon engaging a chain which extends tightly around and on the tank. Simultaneously the wire is fed from a supply spool onto a wire-gripping drum and is then laid on the outer tank wall with a wire tension established by monitoring deviations in stress with respect to a nominal value of stress, and using such deviations to produce changes in the differences in peripheral linear speed between on the one hand the sprocket wheel speed (carriage speed) and on the other hand the linear speed of the wire-gripping drum. Such stress is maintained substantially constant at the same nominal value whereby the wire is uniformly and accurately stressed when and as it is being wrapped around the tank wall. A platform carrying wire tensioning apparatus may be raised or lowered on the carriage during carriage movement, either in the forward direction or in reverse direction or when the carriage is at standstill. Means are incorporated to assure a constant spacing between wire convolutions. Also control means are incorporated to maintain constant tension regardless of carriage speed either in a forward or reverse direction or at carriage standstill. The wire may be laid in a continuous helix or in steps accurately controlled as to height. Also means are incorporated to achieve or maintain an automatic wire tension regardless of carriage movement in either direction of carriage movement or at standstill. Further, the wire may be tensioned from a slack or zero tension condition to any desired tension and maintained automatically at such tension without requiring carriage movement. Also, the desired tension may be preadjusted to any desired value while the carriage is in motion either in the forward or reverse direction. A hydraulicelectrical system is used for these purposes.

United States Patent Dykmans 5 *May 30, 1972 MEANS AND TECHNIQUES USEFUL IN PRESTRESSING CONCRETE STRUCTURES [72] Inventor: Maximiliaan J. Dykmans, 4434 Mayapan Drive, La Mesa, Calif. 92041 1 Notice: The portion of the term of this patent sub sequent to Mar. 30, 1988, has been disclaimed.

[22] Filed: June 24, 1970 [2]] Appl. No.: 49,277

Related US. Application Data [63] Continuation-impart of Ser. No 718.138, Apr. 2,

1968, Pat. No. 3.572596,

[52] U.S.Cl ..242/7.21 [51] Int. Cl. ..B21i 17/00, B6511 81/00 [58] FieldofSearch ..242/7.2l,7.22,7.23

[56] References Cited UNITED STATES PATENTS 3,572,596 3/1971 Dykmans ..242/7.2l 2,159,969 5/1939 Furst ..346/330PTUX 2,321.465 6/1943 Crom... .....242/7.23 X 2,520,402 8/1950 Hirsh .1 24217.22 2.573.793 11/1951 Kennison... 242/722 2.589,366 3/1952 Gauthier.... 242/722 3,281,085 10/1966 Crom 242/121 3,338.527 8/1967 Chidzey.. 242/722 3.379.385 4/l968 Osweiller 242/722 3.477.652 11/1969 Crowley.. 111111 v.242/72] 2.142.252 H1939 Nunan .346/330 PT UX Primary Examiner-Stanley N. (jilreath Assistant Examiner- Milton Gerstein Attorney- Lyon & Lyon [57] ABSTRACT In wrapping wire around a concrete tank to prestress the same, a carriage is caused to travel around the tank by a motor-driven sprocket wheel thereon engaging a chain which extends tightly around and on the tank. Simultaneously the wire is fed from a supply spool onto a wire-gripping drum and is then laid on the outer tank wall with a wire tension established by monitoring deviations in stress with respect to a nominal value of stress, and using such deviations to produce changes in the differences in peripheral linear speed between on the one hand the sprocket wheel speed (carriage speed) and on the other hand the linear speed of the wire-gripping drumv Such stress is maintained substantially constant at the same nominal value whereby the wire is uniformly and accurately stressed when and as it is being wrapped around the tank wall.

A platform carrying wire tensioning apparatus may be raised or lowered on the carriage during carriage movement, either in the forward direction or in reverse direction or when the carriage is at standstill.

Means are incorporated to assure a constant spacing between wire convolutions. Also control means are incorporated to maintain constant tension regardless of carriage speed either in a forward or reverse direction or at carriage standstill. The wire may be laid in a continuous helix or in steps accurately controlled as to height. Also means are incorporated to achieve or maintain an automatic wire tension regardless of carriage movement in either direction of carriage movement or at standstill. Further, the wire may be tensioned from a slack or zero tension condition to any desired tension and maintained automatically at such tension without requiring carriage movement. Also the desired tension may be preadjusted to any desired value while the carriage is in motion either in the forward or reverse direction. A hydraulic-electrical system is used for these urposes.

25 Claims, Drawing Figures PATENTEDHAYQO I972 3. 6651. 1 8 9 sum 2 0F 4 JNVENTOR. MAX/M//AAA/ JDVtM/WS Fla. 2.

MEANS AND TECHNIQUES USEFUL IN PRFSTRFSSING CONCRETE STRUCTURES The present application is a continuation-in-part of my pending US. application, Ser. No. 718,138 filed Apr. 2, 1968, now Pat. No. 3,572,596.

The present invention relates to improved means and techniques which are particularly useful in the prestressing of concrete structures such as, for example, reservoirs, nuclear reactors, pressure vessels in general, and pressure pipes. It will be appreciated that the invention in its broader aspects is useful for other purposes such as, for example, laying cable under controlled tension.

A specific object of the present invention is to provide im proved means and techniques whereby a more uniform and accurate stressing of wire is obtained in the process of wrapping the same around cylindrical structures.

Another specific object of the present invention is to provide a system of this character in which the wire tension is automatically adjusted so as to make such wire tension substantially constant in intensity.

Another specific object of the present invention is to provide a system of this character in which stresses are monitored to derive information as to the condition in the wire and using such information in a manner as to change relative speeds between carriage travel and the rate at which the wire is wrapped to thereby obtain constant tension in the wire during the wrapping process.

Another specific object of the present invention is to provide a system of this character in which a differential mechanism is controlled in accordance with changes in stress so as to minimize variations in such stress.

Another specific object of the present invention is to provide a system of this character incorporating means for assuring accurate spacing of wire convolutions on the tank.

Another specific object of the present invention is to provide an improved control system for achieving controlled movement of a platform on the carriage to achieve a constant predetermined spacing between wound wire convolutions on the tank.

Another specific object of the present invention is to provide a versatile system of this character which provides independent adjustments expediously and without substantial duplication, i.e., various components are used in multi functions such as in producing carriage movements, controlled vertical movements of a platform carrying the wire tensioning apparatus, and controlled wire tensioning regardless of carriage or platform movements or during standstill.

Another specific object of the present invention is to provide an improved system which provides automatic control of wire tension under all conditions.

The features of the present invention, which are believed to be novel, are set forth in particularity in the appended claims. This invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof, may be best understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. I illustrates relationship of apparatus with respect to a concrete wall of a tank around which a carriage effectively pulls itself while laying wire on the tank in a stressed conditron.

FIG. 2 is generally a view in side elevation and partly in diagrammatic form illustrating the wheeled carriage with the vertically adjustable platform carried thereon.

FIG. 3 is an electrical diagram illustrating connections to various components which are mounted on the vertically moveable platform shown in FIGS. 1 and 2.

FIG. 4 illustrates means in which one of the switches shown in FIG. 3 is actuated.

FIG. 5 illustrates the manner in which the individual wire strands S are spaced using the apparatus described herein.

FIG. 6 illustrates a hydraulic control system mounted on the vertically moveable platform in FIGS. 1 and 2.

FIG. 7 illustrates the mechanism, a portion of which is illustrated also in FIG. 2.

In FIGS. 1 and 2, a sprocket chain C encircles the outer wall W of the concrete structure T. The chain C may be considered stationary, particularly since the major length of the same is in nonsliding contact with wall W. The chain C is used to propel the wheeled carriage 7 having wall-engaging wheels 8 and ground-engaging wheels 9. This carriage 7 mounts a platform 5 which is vertically adjustable on carriage 7 and which carries the mechanism for propulsion of the carriage 7 around the wall and for simultaneously laying or wrapping wire or strand S around the wall under tension. As illustrated in FIG. 1, such chain C passes in turn in this order over: guide sprockets 2 and 3, spring-loaded tensioning sprocket 4 urged by spring 4A, drive sprocket 22 on shaft l0 and sprocket wheel 20. The drive sprocket 22 is on shaft 10 which also mounts a larger sprocket wheel 33. A drive chain 32 extends over wheel 33 and sprocket wheel 31 on the output shaft of hydraulic drive motor 30. Thus, it will be seen that operation of motor 30 causes the carriage 7 with platform 5 thereon to move around the circular tank wall W for purpose of wrapping cable, wire, or strand S around such wall.

The wire, strand, cable, or the like, S, which is wrapped around the wall W with tension uniformly and accurately being applied to such cable during such wrapping extends from a supply reel R, which may be mounted on carriage 7, to and around a wire-gripping drum 2] (which is coaxially mounted with the previously mentioned sprocket wheel 20 but which may rotate independently of the same on different shafts 20A, 21A as illustrated in FIG. 2) and then to the structure wall W for prestressing of the same. At the point where the wire S first engages the drum 21, the wire is spring-urged against such drum by device 6 for purposes of assuring a non slip condition between the wire and its gripping drum 21.

The wire-gripping drum has a sprocket wheel 213 secured thereto as illustrated in FIG. 2 with a chain 41 extending over such wheel 21B and a sprocket wheel 42 on shaft 40.

The wire S is tensioned and thus stretched as a result of the lineal speed of the carriage 7 being somewhat greater than the rate at which the wire S is laid on the wall, i.e., assuming that the effective diameters of sprocket wheel 20 and wire drum 21 are the same, as they may be in practice, the sprocket wheel 20 rotates somewhat faster than the wire-gripping drum 21 to cause the wire to be stretched and hence tensioned. For that purpose, rotation of wire drum 21 is impeded in controlled manner.

It is of importance that such tensioning be uniformly and accurately established during the wire wrapping operation; and for that purpose, the system described herein is of particular usefulness.

In FIG. 2, the shaft 10 driven by motor 30 also drives an axle gear of a differential system 82. The other axle gear 84 and a sprocket wheel 15 are on the same shaft 11. A chain 16 passes over sprocket 15, and a sprocket 16A on shaft 40 so that the wire drum sprocket 21B and connected wire drum 2] rotate together at a speed determined by the rotational speed of shaft 40 which is controlled as presently described.

A plurality of spider gears 86, each joumaled for rotation in the differential housing 87, are in mesh with the axle gears 80, 84. A ring gear 89 on housing 87 is in mesh with a gear 98 on the output shaft 96 of a control motor 92. Means 91A may be provided on shaft 96 to limit rotation of ring gear 89 in one direction when power is removed, i.e. to prevent rotation in the opposite direction as described in more detail later.

The control motor 92 is controlled by the output of a servo system 97 having two inputs which are compared in system 97 and functioning to control motor 92 in accordance with such comparison. One of such inputs is a current or voltage derived from a torque transducer 100 associated with shaft 40 in such a manner as to produce such current or voltage that changes in intensity with the torque being applied to shaft 40. The other input is a manually adjustable input derived from the tap 102 on potentiometer resistor 103 having its outside terminals connected to opposite terminals of voltage source 104. As a result of any change in torque in shaft 40, from a nominal value, there is a change in the output of servo system 97 to cause the motor 92 to rotate at a different speed which in turn causes the shaft 40 to rotate at a different speed until the torque sensed by transducer 100 is restored to such nominal value. In other words, a self-balancing system is provided such that the tension of wire S, related to the torque in shah 40 is maintained substantially constant during the operation of the system.

The mechanism previously described for propulsion and controlled wire laying is all mounted on the platform 5. The platform is slidably mounted in the carriage 7 and is vertically adjustable therein so that successive convolutions of wire laid on the tank wall may be of different elevation. Preferably the wire wrapping is started at the bottom off the tank with the platform 5 being raised each time the carriage makes one revolution around the tank.

The platform 5 is held in the position to which it is adjusted by a cable 200 having one of its ends secured to the platform 5 at region 5A and its other end wound around a winch drum after passage over a supporting pulley 203 rotatably mounted on the upper portion of carriage 7 at 7A. This drum 202 is drivable by the output shaft 205 of a hydraulic winch motor 206 which is supplied with hydraulic fluid from pump 207 via hydraulic line 208, solenoid valve 209 and hydraulic lines 210. The pump 207 is driven by the motor 30 via shaft 10, sprocket wheel 212 on shaft 10, chain 214, and the input sprocket wheel 215 of pumps 207. In one position of solenoid valve 209 as explained later, fluid may be returned to the sump 220, in which case the winch drum remains stationary, i.e., the platform 5 remains in a stationary adjusted position when and as the carriage 7 is being propelled by power being applied to motor 30. The winch drum 202 has coaxially mounted therewith for movement therewith, a so-called cam wheel 222 which is preferably of the same diameter as the drum 202 for operation of a control switch LS 2 for purposes described later.

Accurate control of the spacing between adjacent convolutions of wire, i.e., the pitch is achieved using the switches LS 1 and LS 2 in FIG. 2 which are electrically connected with other elements in a pitch control circuit 240 as now described with reference to the lower, left-hand portion of FIG. 3 which shows this pitch control in addition to other electrical circuitry described later.

The switch LS 1 is in the form of a microswitch on carriage 7 and has its actuating element movable into engagement with a stationary post 242 on the ground whereby such switch LS l is actuated at least once per revolution of the carriage 7 around the tank T.

The switch LS 2 as shown in FIGS. 2 and 4 has its actuating element cooperating with the cam wheel 222 which has cams spaced thereon one eighth of an inch apart so that for each one eighth of an inch peripheral movements of the cam 222, the switch LS 2 is operated through an On-Off-On cycle. When as preferred, the diameter ofthe cam wheel 222 is equal to the diameter of the winch drum 202 (FIG. 2) this Aa-inch movement corresponds to one-half of that movement or onesixteenth of an inch movement of platform 5 because of the manner in which it is supported by cable 200.

These switches L8 1 and LS 2 are nonnally closed switches, and each as seen in FIG. 3 are associated with a so-called Eagle type counter device 246 which incorporates a clutch winding 247 and a so-called advance winding or coil 248. The energization of winding 247 results in operation of the normally closed switch 247 A as indicated by dotted line 247 B, and energization of coil 248 results in operation of normally closed switches 248 A and 248 B as indicated by the dotted lines 248 C and 248 D.

The control circuit is energized by 120 V AC. applied between leads L1 and L2.

Switch L8 1 and winding 247 are in series between lines L1 and L2. Switches LS 2, 2488 and coil 248 are in series between lines L1 and L2. Switches 247A and 248A are in a series circuit with relay coil 250 between lines L1 and L2; and when coil 250 is energized, it operates its associated relay switches 250A and 2508 as indicated respectively by dotted lines 250C and 250D. It is noted that the series circuit comprising switches 247 A, 248A is bridged or shunted by a manually operable normally open push button type switch 254, termed a jog switch for obtaining small movement of the platform 5 when the carriage 7 is in movement. Switch 250A when closed energizes the pilot light 256. The other relay switch 250 B is connected in a control circuit for the solenoid valve 209 for control of the platform raising and winch motor 206 (FIG. 2); and for that purpose, the solenoid valve 209 has correspondingly two windings 209 A, 209 B. Either one or neither one of these solenoid valve windings 209 A, 209 B may be selected for energization depending upon the position of a three-position, manually operable selector switch 260 having an "OfF'position, a Raise position, and a "Lower" position. The switch 260 is illustrated in its Raise" position wherein the lead 261 is connected to one terminal of coil 209 A having its other terminal connected to the minus lead 264 of DC power supply 265. In the Lower position, lead 261 is con' nected to one terminal of winding 209 8 having its other terminal connected to lead 264. In the Oi-F position of switch 260, neither one of the windings 209 A, 209 B is energized. This lead 261 is connectable to the other positive lead 267 of source 265 via a two-position manually operable switch 270 having either an Automatic or a "Manual" position. In the Manual position, leads 261 and 267 are interconnected directly; in the Automatic position these two leads 261, 267 are connectable via the previously mentioned relay switch 250 B which is connected in series with the switch 270 in its Automatic" position.

The operation of this pitch control circuit is now described under the condition that switch 270 is adjusted to its Automatic" position and switch 260 is in its Raise position. It will be understood that the counter 246 is of the type which is manually adjustable to respond to and produce a control operation in accordance with each of a predetermined number of pulses applied thereto. Thus the counter, known commercially as an Eagle Cycle-Flex counter, may be adjusted such that the number of counts may be from one to 40 in number, depending upon the desired wire pitch. For example, the desired wire pitch is eleven-sixteenths inch and the counter is manually adjusted to respond in succession to only each of the first I 1 counts or digits developed by the cam disc 222 of the cable winch drum 202 (FIGS. 2 and 4). The counter 246 is automatically reset to its assumed preadjusted count of l 1 upon operation of switch L8 1 by stationary post 242 (FIG. 2). This assures initiation of the pitch control of wire S always on a point on the vertical line 280 (FIG. 5). Once the counter 246 is reset at 280 to the preset count of eleven, the wire S is then no longer laid horizontally as in dicated by the wire distance S1, S2, but the succeeding wire section S2, S3 is inclined due to raising of the platform 5 and when the vertical line 282 is reached (corresponding to point S3) the wire is again laid horizontally without any upward or downward movement being imparted to the platform 5 when and as the carriage 7 is being propelled around the tank T so that consequently the points 53, S4, S5, and S6 are in the same horizontal plane. At point S6 the post 242 again causes the switch LS 1 to be actuated to again allow a lifting of platform 5. This wire pattern illustrated in FIG. 5 is not dependent upon the speed of carriage travel, i.e., the same results regardless of speed of carriage travel or changes in speed of carriage travel or whether or not the carriage may have been in a standstill condition somewhere between lines 280 and 282. This is so because the position of platform 5 is made independent of the position of carriage 7 as a result of using the same prime mover 30 and special pump 207 driven by such motor or engine 30.

Returning to the operation of the pitch control circuit in FIG. 3 opening of switch LS 1 results in energization of clutch 247 and resetting of the counter switch 246 to its assumed preset l I count. This 11 count is counted down one digit at a time each time switch LS 2 is operated (FIG. 4). During this countdown, switch 247A is closed to condition a circuit for relay coil 250. Thus, with switch 247A closed, the relay coil 250 is energized to close switch 2508 to thereby connect solenoid valve raise coil 209A between DC lines 267, 264 in which case hydraulic power is supplied to the winch motor 206 (FIG. 2) which then rotates winch drum 202, and this rotation continues to cause the switch LS 2 to be operated. The first time switch LS 2 is operated, the platform 5 is raised one count, i.e., one-sixteenth inch and the count of the counter switch 246 is reduced from an initial count of l l to the count of i0. After the eleventh count, i.e., the counter reads zero and the switches 248A and 2488 remain open thereby deenergizing relay coil 250 and preventing energization of the solenoid valve. This condition prevails until the carriage 7 is moved around the tank to again operate switch LS1 and thereby reset the counter switch 247 to the preset l l count. Manual override or jogging of the platform may be accomplished to change wire spacing if desired by operating pushbutton switch 254 which causes relay coil 250 to be energized. Such jogging may result in either upward or downward movement of the platform 5 depending upon whether switch 250 is initially adjusted to its Raise" or its Lower position. Selector switch 270 in "Manual position enables a direct manual control through the Raise or Lower" contacts of selector switch 260, even if part or the entire automatic-pitch-control circuit is or becomes inoperable. This means that the amount of pitch can be controlled manually without the use of the automatic pitch control circuit. By simply working the selector switch 260 from its Off position to its Raise position, it is possible to develop manually the required amount of pitch simulatin g the purpose of the automatic pitch control circuit.

It will be appreciated that instead of having only one such post 242, a plurality of such posts may be spaced around the tank T all for the purpose of resetting the counter switch 246 by actuation of switch LS l as previously described. Also, instead of beginning the wire wrapping at the lower portion of the tank and proceeding upwardly, the wrapping may, if desired, be accomplished in a downward direction, in which case the selector switch 260 is in its Lower" position.

It will be further appreciated that the distance between lines 280 and 282 may be decreased or increased as desired and indeed this distance may at one extreme correspond substantially to the circular distance around the tank, in which case the pitch is considered as being of constant inclination without horizontal stretches of the wire. This latter mode of constant inclination may be achieved simply by adjusting switch 270 to its Manual" position. The faster the carriage 7 goes around the tank, the faster proportionally is the platform raised or lowered as the case may be. This is assured by use of a variable control pump 207 whose output is related proportionally to the speed of the motor or engine driven shaft 10. This pump 207 continues to pump hydraulic fluid when the three position switch 260 is in its Off position in which case the fluid is not delivered under pressure to the winch motor 206 but is allowed to return to the sump 220.

Further details of the hydraulic system are illustrated in FIG. 6 where the hydraulic system includes three pumps 300, 301, and 207. Pump 301 is required to have the largest capacity and it serves to supply fluid under pressure to the motor 30 for driving the carriage 7 around the tank. In such case, the fluid flow is from the reservoir 220 through the valve 306 and filter 307 to the inlet of pump 301 and delivered under pressure to the selector valve 309 and forward and reverse valve 310 from whence the fluid is delivered to hydraulic motor 30.

The pump 301 is a so-called stem control pump in that it incorporates a large lever which may be moved manually to produce a continuous change in speed of motor 30 starting from zero speed to maximum speed. The valve 309 is a selector valve which transfers fluid flow either to motor 30 as described above or to the platform winch motor 206 via the solenoid valve 209 in which latter case the platform may be raised or lowered, depending upon the energization of solenoid valve coil 209A or 2098 (FIG. 3) without requiring movement of the tower for that purpose. The fluid in this latter instance flows through valve 309, check valve 315, and through valve 209 to winch motor 206. in this regard, it is noted that the pump 207 is not operating because it requires for its operation movement of the carriage 7, i.e., rotation of shaft 10 which chain drives the sprocket drive 215. Check valve 316 prevents flow from valve 309 to the outlet of pump 207. Jogging of the platform 5 may be accomplished using pushbutton switch 254 or may be moved continuously by adjusting the switch 270 to its Manual position, (FIG. 3).

This large pump 301 is driven by a gasoline engine 320 which serves also to drive the pump 300 for supplying fluid under pressure to the servo motor 92 for the automatic control of wire tensioning and detensioning in the process of winding the wire S under the desired constant tension.

Pump 300 is a pressure compensated pump delivering fluid under substantially constant pressure. The flow of fluid is from reservoir or sump 220 through valve 306 and filter 307, through pump 300, servo valve 332 to the servo motor 92 whose shaft 96 drives the differential system 82 having a rotatable element 11 (FIG. 2) thereof coupled to the wire drum 21B via a shaft 40 in which the torque is sensed by load cell 100.

The servo valve 332 receives an output from amplifier 340 to which a command signal is supplied from potentiometer 103 on control panel 341. Another input to amplifier 340 is the output of preamplifier 343 which receives an input from the torque load cell and provides a signal which is applied to the tension indicator 344 on panel 341. This tension indicator 344 may be of the visual type such as to produce a digital indication, but is preferably a recorder for purposes of achieving an ink permanent record of tension.

A permanent-type paper recorder is illustrated also at 344 in FIG. 3. It may be of the type supplied by Hewlett-Packard with conventional recording paper advancing mechanism which is operated in accordance with a signal applied thereto via leads 350 from the output of amplifier 352 having an input signal developed in accordance with the actuation of switch 360, such switch 360 being a proximity type switch which as shown in FIG. 2 is mounted adjacent to a magnet 36] extending from shaft 40 and is actuated thereby upon rotation of shaft 40. The pulses developed upon actuation of switch 360 are used to move the paper of recorder 344 a distance propor tional to the number of such pulses processed in proximity amplifier 352 so that the distance traveled by the paper upon which a recording is made is a measure of the amount of wire S that has been wound on the tank. The signal recorded is applied to the recording signal input terminal 362, 363. Terminal 362 is connected to the output of amplifier 343 as is also digital meter 344A, the other terminal 363 and the other terminal of meter 344A are connected to an adjustable reference point on resistance 365 which is connected across the load cell power supply 370. Thus, a permanent record is available of the tension present in each portion of the wire as it was wound.

it is noted for the foregoing purposes that the output of amplifier 340 is applied to the servo valve 332 in the normal Run position of the two-position, manually adjustable switch 380 in which case the amplifier output is applied via connected switch contacts, E, F, and U to the terminals 384, 385 of valve 332, in which case either positive or negative voltages as the case may be are continuously applied to valve 332 in the process of maintaining constant wire tension. it is sometimes desirable to adjust this tension manually using a jog-type control and to maintain the same, independently of operation of load cell 100, in which case switch 380 is actuated to its other "Stop position to thereby disconnect the servo valve 332 from the amplifier and to connect lead 390 to terminal 384 via contacts G and H and to connect terminal 385 via switch contacts K and L to the common ground lead 392 and at the same time to apply the command voltage on the tap of command potentiometer 103 via resistances 394, 395 and switch contacts C, D, and E to an output terminal of amplifier 340 by a feedback path which includes a connection between the junction point of resistances 394, 395 to one terminal of amplifier 340. With lead 390 so connected to terminal 384, either a positive or a negative voltage may be applied to such terminal by correspondingly closing the "Forward" jog pushbutton switch 396 or the Reverse" jog pushbutton switch 397 as desired via corresponding speed adjustments resistances 388, 389. Thus, in the Stop" position of switch 300, the tension in the wire may be manually increased or decreased and the tension may be observed on meter 344A and recorded on meter 344.

In normal operation when the carriage 7 is moving and a constant tension is being maintained by the servo system the housing 82 continuously rotates and variations eiflier below or above a nominal speed serves to increase or decrease the tension to restore the tension to its nominal adjusted value. When the carriage 7 is in a standstill condition, i.e., stationary, the housing gear 84 oscillates slightly about a normal stationary position. If there were no leakage in the hydraulic system, there would be no such slight oscillation or hunting."

When maintaining constant tension with carriage movement, there is, of course, a difference in speed between, on the one hand the sprocket and the wire gripping drum 21. Hence, there is a requirement that the differential housing 82 rotate. However, at standstill, when both the sprocket wheel 20 and the wire gripping drum 21 are both stationary, the differential housing is not required to move but there may be some slight movement or oscillation about a zero stationary point because of oil leakage past valves, etc.

FIG. 7 illustrates details of a one way stop mechanism 91A in which the shaft 96 (FIGS. 7 and 2) mounts a disc 918 on which is secured a stop block 91C. During normal wire wrapping, the disc 91B rotates in a clockwise direction as indicated by arrow 91D; but when the carriage speed is reduced to zero, such rotation stops and there is then a tendency for the tension in the previously stressed wire to rotate the shaft 96 in the opposite or counterclockwise direction. For preventing this, a stop member 91B is pivoted at 91F and is urged outwardly by a compression spring 91G having one of its ends bearing against stop lever 91E and the other one of its ends bearing against a stationary abutment 91H. This spring is sufliciently strong and long to prevent engagement of lever 915 with block 91C during clockwise rotation of shaft 96, but when and as the carriage movement is being reduced to zero, as for example in the process of shutting down the system overnight, the lever handle 91.] is manually moved in a clockwise direction about pivot 91F to be positioned behind the block. In so shutting down the system, the tension in the wire is reduced slightly by adjusting the resistance 103. Once the system is so locked off with lever 91E positioned as shown in FIG. 7, changes in resistance 103 which normally cause a lowering of wire tension are no longer effective because the disc 91A is prevented from rotating anticlockwise by lever 915. To unlock the system, the resistance 103 is adjusted for a higher tension than the lock-off tension, in which case the disc 91A rotates clockwise to allow the lever 915 to move away from abutment 9IC under the influence of spring 910.

In certain circumstances it is desired to obtain a rapid engagement or disengagement of the wire from gripping drum 21 and this may be done by operating switch 380 to its "Stop" position and operating jog switches 396 or 397. Important uses, for example, of this jogging control are for purposes of developing maximum speed for threading a new wire strand through the system; tensioning or detensioning wire that has previously been applied to the tank wall and which for some reason or other may be required to be removed and replaced.

In automatic operation, it is noted to increase the wire tension with the carriage 7 moving the differential housing 82 is caused to increase in speed and this is accomplished by adjusting the tension control potentiometer 103. The servo system then functions so that the newly adjusted input voltage is summed with a voltage derived from the load cell and this algebraic sum by action of the system is automatically reduced to zero. Should there be any slippage of the chain on the tank and hence a change in relative speeds such that the tension tends to change, the servo system quickly functions automatically to minimize or nullify any change in wire tension.

An important feature of the present system involves the fact that the wire tension may be adjusted without the need for moving the carriage. With the carriage stationary adjustment of resistance 103 to a different setting, either lower or higher, causes the servo motor 92 to drive the ring gear 89 to cause the wire-gripper drum 21 to move in a corresponding direction. This may be accomplished not only by adjustment of resistance 103 but also by operating the jog switches 396 or 397. In the latter instance, the tension change may be accomplished more rapidly. The differential housing gear 89 is rotated to cause shaft 11 to rotate with, however, shaft 10 remaining stationary.

Another important feature of the system is that wire tension is maintained constant not only during forward wire laying movement of the carriage 7 but also in those instances where the carriage 7 is being moved in the reverse direction as, for example, when it is desired to return to a so-called wire clamp ing off point on the tank wall or to correct wire spacing. In this latter regard, the structure of the wire gripper is of importance, and for that reason, the wire gripper described in my US. Pat. No. 3,510,041, issued May 5, I970 is preferred because lack of wire tension on one side does not destroy the gripping action as is the case, for example, when a conventional capstan or drum is used. Using a wire gripper of the character described in that patent, wire slack may be tolerated.

Another important feature of the present system involves the fact that the platform 5 may be raised or lowered at car riage standstill with full power using the carriage pump 301 and selector valve 309 in its condition wherein it supplies fluid under pressure to motor 206. It is noted again that at standstill, pump 207 does not function because it requires carriage movement for its operation.

It is noted in particular that the vertical movement of platform 5 during horizontal carriage movement may be controlled by setting of the counter 246 (FIG. 3) and/or by adjustment of flow of pump 207 using handwheel control 207A which serves to control or adjust the volume of fluid being supplied to motor 206. The higher the volume of fluid supplied to motor 206 the higher is the speed of vertical platform movement; and hence, the greater the slope of the wire being laid as exemplified by the slope of line 52-83 in FIG. 5. Indeed, when the switch 270 (FIG. 3) is in its "Manual" position the slope of the wire is such that a continuous helix is formed because in such case the counter circuit 246 has no control function, assuming, of course, that the selector switch is in "Raise or "Lower position.

The pump 300 is as indicated previously a pressure regulated or compensated pump for purposes of delivering sufiicient constant pressure under all conditions. The pump 301 is a so-called manually operable stem control pump which through manual adjustment is capable of delivering an oil flow in continuous infinite steps from zero to maximum flow capacity with the flow rate being substantially directly proportioned to the amount of manual stem movement. The pump 207 is a variable volume type pump, the output volume of which may be controlled by a handwheel control 207A and when such handwheel is adjusted, the flow of fluid is directly proportioned to the speed of input sprocket 215 (FIG. 2), i.e. directly proportional to speed of carriage 7. In some cases the handwheel control 207 is adjusted for zero fluid flow in which instance carriage movement produces no vertical movement of platform 5. In other cases, the handwheel control 107A may be adjusted for maximum flow in those instances where it is desired to accomplish a steep raising or lowering of the platform 5.

While a specific embodiment of this invention has been shown and described, it is not intended to limit the same to the exact details of the construction set forth, and it embraces such changes, modifications and equivalents of the parts and their formation and arrangementas come within the purview of the appended claims.

lclaim:

1. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire upply; means on said carriage for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means for producing movement of said movable element such that a tension is developed in said wire; means operating concurrently with said movement producing means for sensing a condition representative of the tension in said wire and developing a first signal; means developing a second signal independently of said first signal but representative of a desired tension in said wire; a servo system responsive to and controlled in accordance with said first and second signals and functioning to produce a control signal representative of the difference in said first signal and said second signal; and means responsive to said control signal and controlling said movement producing means to restore said first signal to a value commensurate with said second signal, a shaft coupled to and rotatable with said movement producing means, and two position means cooperating with said shaft and effective in one of its positions to allow said shaft to rotate in either direction and effective in its other position to prevent rotation in only one direction.

2. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; means for gripping wire supplied thereto from said wire supply; said gripping means including at least one mova ble element; means for moving said carriage around said circular structure; means for producing movement of said movable element such that a tension is developed in said wire; means operating concurrently with said movement producing means for sensing a condition representative of the tension in said wire and developing a first signal; means developing a second signal independently of said first signal but representative of a desired tension in said wire; a servo system responsive to and controlled in accordance with said first and second signals and functioning to produce a control signal representative of the difference in said first signal and said second signal; and means responsive to said control signal and controlling said movement producing means to restore said first signal to a value commensurate with said second signal, a platform, means mounting said platform for vertical movement on said carriage, said wire gripping means being mounted on said platform, means for changing the elevation of said platform on said carriage, and means coupling said changing means to said carriage moving means such that said carriage and said platform move at proportionate rates.

3. A system as set forth in claim 2 including means for initiating operation of said coupling means at a predetermined location of the carriage and for disabling the same prior to completion of travel of the carriage around the tank.

4. A system as set forth in claim 2 including adjustable means for coupling said carriage moving means directly to said platform changing means to the exclusion of said carriage such that said platform may be moved without requiring movement of the carriage.

5. A system as set forth in claim 3 including means responsive to actual extent of platform movement for disabling said coupling means.

6. A system as set forth in claim 5 including means for presetting said actual extent and means for adjusting the last mentioned means.

7. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; means on said carriage for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means for producing movement of said movable element such that a tension is developed in said wire; means operating concurrently with said movement producing means for sensing a condition representative of the tension in said wire and developing a first signal; means developing a second signal independently of said first signal but representative of a desired tension in said wire; a servo system responsive to and controlled in accordance with said first and second signals and functioning to produce a control signal representative of the difference in said first signal and said second signal; and means responsive to said control signal and controlling said movement producing means to restore said first signal to a value commensurate with said second signal, and means on said carriage for indicating the value of said tension.

8. A system as set forth in claim 7 wherein said indicating means includes recording means having a movable recording medium and means for producing a recording thereon, means coupling said medium to said element for movement therewith, and means actuating said recording producing means in accordance with a signal derived from said tension sensing means.

9. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; a platform movable vertically on said carriage; means on said platform for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means for moving said platform vertically on said carriage; means for producing movement of said movable element such that a tension is developed in said wire; means monitoring a condition of stress developed in said system and producing a first signal in accordance with such stress; means developing a reference signal means operating in accordance with the joint action of said first and reference signals and developing a bidirectional control signal, a control motor controlled in accordance with said control signal and having an output shaft; means coupling said output shaft to said one movable element; and adjustable means cooperating with said output shaft and having two positions, one of which allows said output shaft to rotate in either direction and the other of which prevents rotation of said output shaft in one direction only.

10. In a system of the character described wherein a can riage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; a platform movable vertically on said carriage; means on said platform for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure either in the forward or reverse direction; means for moving said platform vertically on said carriage; means controlling movement of said movable element such that a tension is developed in said wire; said means for moving said platform including a coupling between said carriage moving means and such platform such that the carriage and platform move at proportionate rates.

11. A system as set forth in claim wherein said carriage moving means includes a carriage motor and a first pump for supplying energy to said motor; said platform moving means including a platform motor; and a second pump driven by said carriage to supply energy to said platform motor.

12. A system as set forth in claim 11 including selector valve means to either communicate said first pump to said carriage motor or to said platform motor.

13. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; a platform movable vertically on said carriage; means on said platform for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means for moving said platform vertically on said carriage; means controlling movement of said movable element such that a tension is developed in said wire; and means responsive to the amount of vertical movement of said platform and controlling said platform moving means.

14. A system as set forth in claim 13 wherein the last mentioned means is automatically rendered effective when and as said carriage reaches a predetermined position and is disabled after said platform is moved vertically a predetermined distance.

15. A system as set forth in claim 13 including means for disabling the last recited means and for rendering said carriage moving means effective to operate said platform moving means.

16. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; a platform movable vertically on said carriage; means on said platform for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means for moving said platform vertically on said carriage; means controlling movement of said movable element such that a tension is developed in said wire.

17. A system as set forth in claim 16 including means for rendering the last mentioned means ineffective and for producing incremental movement of said platform.

18. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; means for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means controlling movement of said movable element such that a tension is developed in said wire; the last mentioned means including a differential system including a first axle gear; a second axle gear, and a ring gear coupled to said first and second axle gears; a motor having an output shaft coupled to said ring gear; a one-way stop associated with said shaft to limit movement of said shaft in one direction only; said first axle gear being connected to said carriage moving means; said second axle gear being coupled to said movable element.

19. A system as set forth in claim 18 including means responsive to tension developed in said wire for controlling said motor. I

20. A system as set forth in claim 18 including means for moving said carriage either in the forward or in the reverse direction.

2]. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; means for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means controlling movement of said movable element such that a tension is developed in said wire; and means on said carriage for indicating the tension developed in said wire.

22. A system as set forth in claim 21 in which said indicating means includes a recording medium, means for moving said recording medium in accordance with movement of said movable element and means for simultaneously making a record on said medium in accordance with tension in said wire.

23. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; a platform movable vertically on said carriage; means on said platform for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means for moving said platform vertically on said carriage; means controlling movement of said movable element such that a tension is developed in said wire; means for producing forward and reverse movement of said carriage moving means, and means for producing either up or down movement of said platform; means for disabling said carriage moving means; means for disabling said platform moving means.

24. A system as set forth in claim 23 including means for automatically maintaining constant tension in said wire regardless of up or down movement of said platform or forward or reverse movement of said carriage.

25. A system as set forth in claim 23 in which said gripping means is effective to grip said wire regardless of movement of said carriage moving means. 

1. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; means on said carriage for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means for producing movement of said movable element such that a tension is developed in said wire; means operating concurrently with said movement producing means for sensing a condition representative of the tension in said wire and developing a first signal; means developing a second signal independently of said first signal but representative of a desired tension in said wire; a servo system responsive to and controlled in accordance with said first and second signals and functioning to produce a control signal representative of the difference in said first signal and said second signal; and means responsive to said control signal and controlling said movement producing means to restore said first signal to a value commensurate with said second signal, a shaft coupled to and rotatable with said movement producing means, and two position means cooperating with said shaft and effective in one of its positions to allow said shaft to rotate in either direction and effective in its other position to prevent rotation in only one direction.
 2. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; means for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means for producing movement of said movable element such that a tension is developed in said wire; means operating concurrently with said movement producing means for sensing a conditIon representative of the tension in said wire and developing a first signal; means developing a second signal independently of said first signal but representative of a desired tension in said wire; a servo system responsive to and controlled in accordance with said first and second signals and functioning to produce a control signal representative of the difference in said first signal and said second signal; and means responsive to said control signal and controlling said movement producing means to restore said first signal to a value commensurate with said second signal, a platform, means mounting said platform for vertical movement on said carriage, said wire gripping means being mounted on said platform, means for changing the elevation of said platform on said carriage, and means coupling said changing means to said carriage moving means such that said carriage and said platform move at proportionate rates.
 3. A system as set forth in claim 2 including means for initiating operation of said coupling means at a predetermined location of the carriage and for disabling the same prior to completion of travel of the carriage around the tank.
 4. A system as set forth in claim 2 including adjustable means for coupling said carriage moving means directly to said platform changing means to the exclusion of said carriage such that said platform may be moved without requiring movement of the carriage.
 5. A system as set forth in claim 3 including means responsive to actual extent of platform movement for disabling said coupling means.
 6. A system as set forth in claim 5 including means for presetting said actual extent and means for adjusting the last mentioned means.
 7. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; means on said carriage for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means for producing movement of said movable element such that a tension is developed in said wire; means operating concurrently with said movement producing means for sensing a condition representative of the tension in said wire and developing a first signal; means developing a second signal independently of said first signal but representative of a desired tension in said wire; a servo system responsive to and controlled in accordance with said first and second signals and functioning to produce a control signal representative of the difference in said first signal and said second signal; and means responsive to said control signal and controlling said movement producing means to restore said first signal to a value commensurate with said second signal, and means on said carriage for indicating the value of said tension.
 8. A system as set forth in claim 7 wherein said indicating means includes recording means having a movable recording medium and means for producing a recording thereon, means coupling said medium to said element for movement therewith, and means actuating said recording producing means in accordance with a signal derived from said tension sensing means.
 9. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; a platform movable vertically on said carriage; means on said platform for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means for moving said platform vertically on said carriage; means for producing movement of said movable element such that a tension is developed in said wire; means monitoring a condition of stress developed in said system and producing a first signal in accordance with such stress; means developing a reference signal means operating in accordance with the joint action of said first and reference signals and developing a bidirectional control signal, a control motor controlled in accordance with said control signal and having an output shaft; means coupling said output shaft to said one movable element; and adjustable means cooperating with said output shaft and having two positions, one of which allows said output shaft to rotate in either direction and the other of which prevents rotation of said output shaft in one direction only.
 10. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; a platform movable vertically on said carriage; means on said platform for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure either in the forward or reverse direction; means for moving said platform vertically on said carriage; means controlling movement of said movable element such that a tension is developed in said wire; said means for moving said platform including a coupling between said carriage moving means and such platform such that the carriage and platform move at proportionate rates.
 11. A system as set forth in claim 10 wherein said carriage moving means includes a carriage motor and a first pump for supplying energy to said motor; said platform moving means including a platform motor; and a second pump driven by said carriage to supply energy to said platform motor.
 12. A system as set forth in claim 11 including selector valve means to either communicate said first pump to said carriage motor or to said platform motor.
 13. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; a platform movable vertically on said carriage; means on said platform for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means for moving said platform vertically on said carriage; means controlling movement of said movable element such that a tension is developed in said wire; and means responsive to the amount of vertical movement of said platform and controlling said platform moving means.
 14. A system as set forth in claim 13 wherein the last mentioned means is automatically rendered effective when and as said carriage reaches a predetermined position and is disabled after said platform is moved vertically a predetermined distance.
 15. A system as set forth in claim 13 including means for disabling the last recited means and for rendering said carriage moving means effective to operate said platform moving means.
 16. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around Said circular structure; a wire supply; a platform movable vertically on said carriage; means on said platform for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means for moving said platform vertically on said carriage; means controlling movement of said movable element such that a tension is developed in said wire.
 17. A system as set forth in claim 16 including means for rendering the last mentioned means ineffective and for producing incremental movement of said platform.
 18. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; means for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means controlling movement of said movable element such that a tension is developed in said wire; the last mentioned means including a differential system including a first axle gear; a second axle gear, and a ring gear coupled to said first and second axle gears; a motor having an output shaft coupled to said ring gear; a one-way stop associated with said shaft to limit movement of said shaft in one direction only; said first axle gear being connected to said carriage moving means; said second axle gear being coupled to said movable element.
 19. A system as set forth in claim 18 including means responsive to tension developed in said wire for controlling said motor.
 20. A system as set forth in claim 18 including means for moving said carriage either in the forward or in the reverse direction.
 21. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; means for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means controlling movement of said movable element such that a tension is developed in said wire; and means on said carriage for indicating the tension developed in said wire.
 22. A system as set forth in claim 21 in which said indicating means includes a recording medium, means for moving said recording medium in accordance with movement of said movable element and means for simultaneously making a record on said medium in accordance with tension in said wire.
 23. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; a platform movable vertically on said carriage; means on said platform for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means for moving said platform vertically on said carriage; means controlling movement of said movable element such that a tension is developed in said wire; means for producing forward and reverse movement of said carriage moving means, and means for producing either up or down movement of said platform; means for disabling said carriage moving means; means for disabling said platform mOving means.
 24. A system as set forth in claim 23 including means for automatically maintaining constant tension in said wire regardless of up or down movement of said platform or forward or reverse movement of said carriage.
 25. A system as set forth in claim 23 in which said gripping means is effective to grip said wire regardless of movement of said carriage moving means. 